Corneal biomechanical properties after SMILE versus FLEX, LASIK, LASEK, or PRK: a systematic review and meta-analysis

Abstract

Background The aim of this study was to compare the postoperative corneal biomechanical properties between small incision lenticule extraction (SMILE) and other corneal refractive surgeries. Methods A systematic review and meta-analysis were conducted. Articles from January 2005, to April 2019, were identified searching PubMed, EMBASE, Web of Science, and International Clinical Trials Registry Platform. Studies that compared SMILE with other corneal refractive surgeries on adult myopia patients and evaluated corneal biomechanics were included. Multiple effect sizes in each study were combined. Random-effects model was conducted in the meta-analysis. Results Twenty-two studies were included: 5 randomized controlled trials (RCTs), 9 prospective and 6 retrospective cohort studies, and 2 cross-sectional studies. Using the combined effect of corneal hysteresis (CH) and corneal resistance factor (CRF), which were obtained from ocular response analyzer (ORA), the pooled Hedges’ g of SMILE versus femtosecond laser-assisted in situ keratomileusis (FS-LASIK) was 0.41 (95% CI, 0.00 to 0.81; p = 0.049; I 2 = 78%), versus LASIK was 1.31 (95% CI, 0.54 to 2.08; p < 0.001; I 2 = 77%), versus femtosecond lenticule extraction (FLEX) was − 0.01 (95% CI, − 0.31 to 0.30; p = 0.972; I 2 = 20%), and versus the group of photorefractive keratectomy (PRK) and laser-assisted sub-epithelial keratectomy (LASEK) was − 0.26 (95% CI, − 0.67 to 0.16; p = 0.230; I 2 = 54%). The summary score of Corvis ST (CST) after SMILE was comparable to FS-LASIK/LASIK with the pooled Hedges’ g = − 0.05 (95% CI, − 0.24 to 0.14; p = 0.612, I 2 = 55%). Conclusions In terms of preserving corneal biomechanical strength after surgeries, SMILE was superior to either FS-LASIK or LASIK, while comparable to FLEX or PRK/LASEK group based on the results from ORA. More studies are needed to apply CST on evaluating corneal biomechanics after refractive surgeries. Electronic supplementary material The online version of this article (10.1186/s12886-019-1165-3) contains supplementary material, which is available to authorized users.

Depth-Dependent Corneal Biomechanical Properties in Normal and Keratoconic Subjects by Optical Coherence Elastography

“…54 SMILE has been shown in theoretical, computational, and clinical studies to confer a relative biomechanical advantage over LASIK by preserving anterior stromal fiber continuity in normal eyes. [55][56][57] In cases where anterior stromal strength is selectively compromised, however, the margin of that advantage would be lower, and in cases where anterior properties are actually weaker than posterior properties (k a /k p <1, as was the case for several KC eyes in this study), photorefractive keratectomy would likely confer even greater stability advantages over LASIK and SMILE by ablating weaker stromal tissue that is less capable of effective load bearing. Since current clinical methods of biomechanical measurement do not provide the spatial contrast necessary to detect localized changes like those described in this series, approaches such as OCE that do incorporate such capabilities are an important focus of translational efforts.…”

SMILE – Small Incision Lenticule Extraction

“…Zahlreiche Studien untersuchten in vivo mittels Ocular Response Analyzer (Reichert, Dephew, NY, USA) oder des Corvis ST (Oculus Optikgeräte, Wetzlar) die Verformung der Hornhaut infolge eines kurzen Luftstoßes zum Rückschluss auf die korneale Biomechanik [57]. Einige Studien zeigten Vorteile für die SMILE, während andere keine Unterschiede zwischen SMILE und Femto-LASIK fanden [58].…”

Longitudinal imaging and femtosecond laser manipulation of the liver: How to generate and trace single-cell-resolved micro-damage in vivo

“…This can induce precise, abrupt, and complete destruction of the tissue through the formation of a cavitation bubble [19,20]. Due to its precision, reliability and reproducibility in homogenous materials, this process is, for instance, used for refractive surgery of the cornea [21] and is therefore very promising for targeted damage induction in other organic tissues.…”